Display element

ABSTRACT

A magnetically operated display element comprises a disc of substantially non-magnetic material, provided on opposite sides with ears extending transversely in the same direction relative to the disc, said ears being designed to allow the pivotal mounting of said disc on supporting means. The disc is contrastingly colored on opposite surfaces and shaped so that concavities are provided as viewed on one of said surfaces, such concavities being on opposite sides of and defining on the surface on which they appear a ridge extending across said disc approximately parallel to the pivotal axis of the disc; the concavities and ridge appearing on the opposite surface as convexities and a valley.

This invention relates to the construction of a display element.

The display element described herein will be used in electromagneticallyoperated displays. The type of display is shown generally in suchpatents as:

U.s. pat. No. 3,140,553 dated July 14, 1964

U.s. pat. No. 3,283,427 dated Nov. 8, 1966

U.s. pat. No. 3,295,238 dated Jan. 3, 1967

U.s. pat. No. 3,365,824 dated Jan. 30, 1968

U.s. pat. No. 3,303,494 dated Feb. 7, 1967

U.s. pat. No. 3,624,941 dated Dec. 7, 1971

These patents disclose the mounting and operation of display elementsoppositely colored on opposite sides which are pivotably mounted, carrya magnet for rotation therewith extending traversely to the pivotalaxis, and have their orientation controlled by the application of amagnetic field exterior to the element.

Although the device described above have utility with large and smalldisplay elements, the invention to be described is of more likelyapplication where the display elements are of relatively large size,i.e. of 11/4 inch diameter or larger.

Such display elements have been made of thin nonmagnetic materials,usually metal or plastic, generally, but not necessarily circular inshape and provided with a pair of ears on opposite sides extending inthe same direction generally transverse to the plane of the disc andprovided with means for the pivotal mounting of the disc, such meansusually comprising apertures in the ears to receive a shaft threadedtherethrough. A magnet mounted for rotation with the disc allows itscontrol by an exterior field.

It has been found that such elements, particularly those of large size,have tended, in ambient light and heat, to differentially expand becausethe darker side absorbs heat at a faster rate than the lighter. With aflat disc, this has tended to warp the disc and, to the extent that suchwarpage has taken place about a bend line transverse to the pivotalaxis; has, by interferring with or misaligning the pivotal mountings ofthe elements, tended to interfere with the free pivotting of the elementon its pivotal axis.

In accord with this invention, the flat form of the disc (contrastinglycoloured on opposite surfaces) is shaped to provide slight spaceddepressions or concavities on one of the surfaces (resulting incomplementary convercities on the other surface). The concavities on onesurface define between them a raised ridge and also constitute theperiphery of the disc as a raised portion relative to the depressions.The opposite surface of the disc is, of course, of complementary formwith a valley extending across the disc corresponding to the ridge. Theresultant shape of the disc which is like a shallow W, when viewed incross-section and along the pivotal axis, acts to prevent warpage ordistortion of the disc under differential expansion or stresses,particularly in directions (i.e. about bend lines having a componenttransverse to the pivotal axis) which would otherwise tend to deflectthe pivotal mountings relative to each other. The shaping of the disc,as described, also acts to strengthen the disc against differentialexpansion in other directions and in general to strengthen the disc.

An alternative to the form shown may be provided where the disc,provided with ears and magents as shown, is not provided with thedepressions discussed above but merely shaped to form a diametricallyextending ridge extending approximately parallel to the intended axialdirection. Although such disc with the ridge only is not as strong inall dimensions as the embodiment of FIGS. 1 and 2, channel effectprovided by the ridge reduces bending of the disc about a lineperpendicular to the shaft.

In drawings which illustrate a preferred embodiment of the invention:

FIG. 1A shows an element pivotally mounted, on a shaft;

FIG. 1B shows the other side of the element of FIG. 1A; and

FIG. 2 shows a cross-section along the lines 2-2 of FIG. 1.

In the drawings, a metal disc is preferably made of aluminium andalthough the exact range of thickness is not critical, I prefer to usealuminium of 5/1000 of an inch in thickness. Magnesium or othernon-magnetic metals in thin form may be also used. Plastic materials mayalso be used. The materials used should, however, be substantiallynon-magnetic, since magnetic material would otherwise tend to distort ornullify the effects of the rotating magnet mounted for rotation with theelement.

With the metal disc 10 shown, pivotal mounting means are preferablyprovided in the form of ears 12 extending from the material of the discand each bent to extend transversely from the disc in the same directionrelative thereto and to provide opposed pivotal mountings 14 as shown,along an approximate centre line of the disc. The ears 14 are used toprovide the pivotal mounting of the disc and are apertured so that amounting shaft 16 may be threaded therethrough to rotatably mount theelement.

Alternative pivotal mounting means are available and will be in somecases used particularly with discs formed of plastic. Such alternativespivotal mountings are considered within the scope of the invention; andthe criterion so far as the invention is concerned being that thepivotal mounting means defines an axis approximately parallel to a lineextending approximately centrally across the disc.

The disc will mount a magnet 18 defining a magnetic axis M-M extendingtransverse to the rotational axis. The magnet may be mounted in variousways and the alternatives are considered within the scope of theinvention. However, in the embodiment show, the magnet is attached toone of the ears 12 for rotation therewith is oriented to define amagnetic axis which is perpendicular to the pivotal axis and to thedisc.

The disc 10 is oppositely coloured on opposite surfaces. It ispreferred, for improved appearance of an array of such elements, tocolor more darkly the side on which the ears 12 extend, and the oppositeside more brightly. In the interest of illustrating the structure of thedevice no indication of colour is given on the drawings. However, thedarker side is usually a dull black while the brighter side may be suchcolours as white, red, orange, yellow or green and these may be of thefluorescent type. One of the surfaces of the disc (here the sideopposite to the one on which the ears extend) is provided with a pair ofconcavities 19 which are located on each side of and define between thema raised portion or ridge 20 extending across the centre of the disc.Thus the concavities are each surrounded by the relatively raised centreline and the relatively raised periphery 21 of the disc. As illustratedin FIG. 1A the brighter side of the disc (the right side in FIG. 2) isthus provided with two convexities bordered by a centre line depressionor valley (the complement of ridge 20) and a lowered periphery. Althoughthe light and dark colouring together with the contouring of the facescould be reversed and still achieve the objects of the invention, thearrangement shown proved that the valley formed on one side of the discfaces the pivot axis and provides clearance for the pivot shaft.

The disc thus shaped, may be formed from aluminium and shaped in asingle stamping and shaping operation or in two separate operations. Ina disc of plastic, the shape might be imparted to the device in themolding operation.

However, the invention extends to the shape produced whatever theforming method used.

The shaping of the disc described provides strength therefor in alldimensions. Moreover, as will be noted in FIG. 2, viewed along thepivotal axis, the disc forms a flat W in centre cross-section. When thedisc is subject to heat through convection or ambient radiation, thedifferential thermal expansion of the disc material will increase thesharpness of some and decrease the sharpness of others of the W folds.Thus differential expansion may increase the channel effect of one oranother of the folds which folds provide rigidity in the disc againstbending along lines having components transverse to the pivotal axis.Misalignment of the pivotal axis is thus avoided. It will be noted thatthis advantageous effect of the spaced concavities is of value even ifthe bearings are otherwise constructed than is shown on the preferredembodiment.

Moreover, the depressions 19 form a relatively raised edge 21 about theedge of the disc best shown in FIG. 2, which forms an additionalreinforcing channel.

Alternatively a simpler disc to that shown in FIGS. 1 and 2 having theears and magnets as shown, formed without the depressions but to providea diametrically extending ridge extending approximately parallel to theextended axial direction. Although such disc with the ridge only is notas strong in all dimensions as the embodiment of FIGS. 1 and 2, thechannel effect provided by the ridge reduces bending of the disc about aline perpendicular to the shaft.

I claim:
 1. A disc of substantially non-magnetic material, provided onopposite sides with ears extending transversely in the same directionrelative to the disc, said ears being designed to allow the pivotalmounting of said disc on supporting means, said disc being contrastinglycolored on opposite surfaces said disc being shaped so that two spacedconcavities are provided as viewed on one of said surfaces, saidconcavities being on opposite sides of and defining on the surface onwhich they appear a ridge extending across said disc approximatelyparallel to the pivotal axis of the disc, said concavities and ridgeappearing on the opposite surface as convexities and a valley.
 2. A discas claimed in claim 1 formed so that the side defining said valley facesthe pivotal axis and said valley is located to provide clearance betweensaid disc material and the shaft located on said pivotal axis.
 3. A discof thin substantially non-magnetic material, means for pivotallymounting said disc for rotation about a pivotal axis roughly parallel toa line across said disc approximately centred thereon, said disc beingcoloured contrastingly on opposite surfaces, said disc being shaped toform a pair of concavities on one of said surfaces, said concavitiesbeing on opposite sides of and defining a ridge extending across saiddisc approximately parallel to the rotational axis, whereby the oppositesurface of said disc is shaped to provide convexities with a valley inbetween.
 4. A disc as claimed in claim 3 wherein the disc is orientedand shaped so that such valley faces and provides clearance between thedisc material and the pivotal axis.
 5. A disc of substantiallynon-magnetic material, provided on opposite sides with ears extendingtransversely in the same direction relative to the disc, said ears beingdesigned to allow the pivotal mounting of said disc on supporting means,said disc being contrastingly coloured on opposite surfaces, said discbeing shaped to provide on one side a ridge, and on the other side avalley, extending across said disc approximately parallel to the pivotalaxis of the disc.